Objective: The immediate and long-term effects of traumatic exposure and subsequent posttraumatic stress reactions in people in high-risk occupations are well-documented. What is less evident is the impact of this traumatic exposure and subsequent traumatic stress symptoms on workers' response to acute stress situations. This study aimed to examine the association between prior traumatic exposure related to policing, current posttraumatic stress symptoms and biological markers of stress, and subjective appraisal of stress before, during, and after exposure to acutely stressful stimuli. Method: A stressful policing situation was created through the use of a video simulator room. Participants' responses to the simulated emergency were evaluated by monitoring heart rate, collecting salivatory samples for cortisol analysis, and repeated administration of a subjective measure of anxiety. Results: Biological indicators of stress, as measured by cortisol level and heart rate, were not associated with previous trauma exposure or trauma symptoms; however, biological response was associated with subjective anxiety. Vulnerability to psychological stress responses during an acute stress situation was also associated with lower levels of social support, previous traumatic exposures, and preexisting symptoms of traumatic stress. The importance of these factors became more pronounced as time progressed after the event. Conclusion: Previous trauma exposure did not put individuals at increased risk of biological distress during an acute stress situation. However, previous trauma and reduced social supports were associated with continuing psychological distress, confirming previous research and raising concerns about the cumulative negative effects of traumatic exposure on psychological health in emergency responders.